Separation of mica from clay by froth flotation

ABSTRACT

Mica, present as an impurity in kaolin clay, is removed from the clay by froth flotation in an alkaline pulp with a complex phosphate ester of a nonionic surfactant of the ethylene oxideadduct type, using an aluminum salt to activate the flotation of the mica.

United States Patent [191 Yan A r. 16 1974 [S4] SEPARATION OF MICA FROMCLAY BY 3,037,627 6/1962 Nazen 209/167 X FROTH FLOTATION 3,259,2377/1966 Scheld 209/166 X 3,329,265 7/1967 Browning t 209/166 Inventor:David g, Edlson, 3,462,013 8/1969 Mencade 209/166 x 3,480,143 11/1969Mitzwajer.... 209/166 [73] Assgnee' 2:53:12 ?'xggg fi gg g'g 3,567,6363/1971 Katzenstein 252/32 .1

6 FOREIGN PATENTS OR APPLICATIONS [22] Ffled' June 2 1,044,733 11/1958Germany 209/166 [21] Appl; No.: 266,159

Primary Examiner-Robert Halper [52] U S 209/166 252/61 Attorney, Agent,or 'Firm-Melvin C. Flint; Inez L.

51 int. c1 B0311 1/02 Msene [58] Fleld of Search 209/166, 5l;O265/g68lI;ABSTRACT Mica, present as an impurity in kaolin clay, is removed 5References Cited from the clay by froth flotation in an alkaline pulpUNITED STATES PATENTS with a complex phosphate ester of a nonionicsurfactant of the ethylene oxide-adduct type, using an alumigz igg 2?num salt to activate the flotation of the mica. 3:009:570 11/1961Lancaster 209/5 5 Claims, N0 Drawings SEPARATION OF MICA FROM'CLAY BYFROTH: FLOTATION BACKGROUND OF THE INVENTION High purity kaolin clay iswidely used as a coating pigment for paper and paints. Such pigmentsmust be free from abrasive impurities, of which mica is an example. Thepresence of mica in more than trace quantity may render the clayunsatisfactory for use as a pigment.

Mica can be removed from clay with reasonable. ease by gravimetric meansor flotation when the clay is coarse. However, when the clay particlesand micaceous impurities are fine, the separation is very difficult.Froth flotation with conventional ionic collectors is usuallyunsuccessful because mica and kaolin, both silicate minerals, havesimilar flotation properties.

THE INVENTION An object of the invention is to provide a novel methodfor removing finely divided mica from finely divided kaolin clay byfroth flotation.

' A specific object is to provide a novel collector system for floatingmica from kaolin clay.

Briefly stated, in accordance with the present invention, a micaceousimpurity, especially muscovite mica, is'removed from kaolin clay bydeflocculating a pulp of the impure clay, preferably activating the micawith an aluminum salt, and subjecting the ore pulp to froth flotation inan alkaline flotation circuit in the presence of a complex phosphateester, or salt thereof, of a nonionic surface active ethylene orpropylene oxide adduct.

PRIOR ART DETAILED DESCRIPTION in putting the invention into practice,the impure clay ore is blunged in water. Coarse grit and undispersibleagglomerates are removed in conventional manner, e.g., by sedimentation,or by treatment in sand boxes.

A clay dispersant (deflocculant) is added before or after degritting.The dispersant used may vary with the nature of the clay. Examples ofdispersants are soda ash, sodium silicate, sodium lignosulfonate andsodium condensed phosphates, alone or in combination. Good results havebeen realized when soda ash was added to adjust pH to a value within therange of9 to l l and sodium silicate. phosphate or lignosulfonate wasadded to deflocculate the pulp and depress the clay.

Water soluble aluminum salts. e.g.. aluminumchloride. nitrate orsulfate, are used in carrying out the invention in order to activate themica. The salts are added as aqueous solutions to the deflocculatedalkaline pulps and mixed therewith before adding the collector. Smallquantities of aluminum salts are used.

e.b., A to 1 lb./ton, usually A 1b./ton. The aluminum salt can beincorporated into the pulp before or after the phosphate ester collectoris added.

The phosphate esters of nonionic surface active agents which are used ascollectors in carrying out the invention are described in U. S. Pat. No.3,567,636 to Katzenstein. The pertinent disclosures in the Katzensteinpatent as to the composition of such esters and to their preparation areincorporated herein by reference. Briefly, these are complex phosphateesters (or salt thereof) of a nonionic surface active compound, thephosphate being selected from the group consisting of monoesters,diesters and mixtures thereof, the nonionic surface active compoundbeing the condensation product of an organic hydroxy compound of from 8to carbon atoms selected from the group consisting of alkyl phenol andalkanols with at least 1 mole of an alkylene oxide having from 2 to 3carbon atoms, the nonionic surface active compound containing a maximumof about 50 percent by weight of alkylene oxide based on the weight ofthe nonionic surface active compound.

The phosphate esters are commercially available under the trade nameGAFAC and are anionic surfactants. The commercial products are usuallymixtures of monoand di-esters. The product GAFAC RO-310 is understood tobe a mixture of monoester and diester, principally diester. Themonoester constituent may be described by the formula:

wherein R oleyl; and n is 4 to 5.

The diester constituent has the formula:

wherein R oleyl, n is 4 to 5.

Obviously the ester can be used in salt form (e.g., sodium, ammonium,calcium, magnesium). in use the acid would be converted to alkali metalsalt form in the basic clay pulp.

Generally, the ester is used in amount within the range of 0.1 to 3lbs/ton, usually within the range of about 0.5 to 1.5 lb./ton.

The phosphate esters normally provide adequate frothing. In some cases,a small amount of a conventional frother such as methyl isobutylcarbinolor pine oil may be added to improve the froth.

Flotation may be carried out at solids within the range of about 5percent to 50 percent, preferably 20 percent to 45 percent solids.

After flotation the clay in the tailings may be fractionated inconventional manner to recover one or more fine size fractions ofbeneficiated clay. in some cases, the fine fractions are lower in micathan the flotation tailings.

The following example is given for illustrative purposes and is not tobe considered as limiting upon the invention.

The clay used in the test was a kaolin from France. The principalimpurity in the clay was muscovite. The degritted minus 325 mesh (Tyler)portion of the impure clay analyzed 2.67 percent K 0, corresponding to22.6 percent muscovite.

A sample of the crude clay (9,000 gm., dry basis) was blunged indeionized water at about 35 percent solids for minutes. The slip wasscreened on a Sweco vibratory screen and the minus 325 mesh fraction ofthe slip was recovered.

The degritted slip (minus 325 mesh fraction) was charged to a Fagergrenconditioner at percent solids. Soda ash was added in amount of 1.0lb./ton and the slip was conditioned for 1 minute. The pH was 1 1.0.Sodium lignin sulfonate was added in amount of 0.5 lb./ton, followed byconditioning for 6 minutes. Aluminum chloride was added in amount of 0.5lb./ton (calculated as AlCl '6H O), followed by 2 minutes conditioning.GA'FAC RO-3l0, 0.5 lb./ton, was incorpo' rated, followed by 6 minutesconditioning. The pH of the conditioned pulp was I 1.0.

The conditioned pulp was transferred to a Denver flotation machine andthe froth was collected. The froth (mica concentrate) and tailings(purified kaolin) were recovered and analyzed. Results are summarized intable form.

Metallurgical results in the table show that froth flotation of the pulpof the impure clay with a phosphate ester complex as the collectorreduced the mica content of the clay from 22.6 percent to 12.3 percentat a clay recovery of about 62 percent.

FLOTATlON OF. MUSCOVITE FROM KAOLIN WITH COMPLEX PHOSPHATE ESTERCOLLECTOR Flotation Muscovitc Distribution of Product Wt. "/1 "/1 K- .OMica, "/r Mica, 7:

Head 100.0 2.07 i 22.0 100.0 Froth Product 37.8 4.67 39.6 66.2 Tuilings62.2 1.45 12.3 33.8

* Calculated I claim:

nonionic alkylene oxide adduct being the condensation product of anorganic hydroxy .compound containing from 8 to 50 carbon atoms andselected from the group consisting of alkyl phenol and alkanol with atleast 1 mole of an alkylene oxide having 2 to 3 carbon atoms, saidnonionic alkylene oxide adduct containing a maximum of about 50% byweight of alkylene oxide.

2. The process of claim i wherein said aluminum salt is added to thepulp before adding said complex phosphate ester.

3. The process of claim 2 wherein the flotation is carried out at a pHwithin the range of 9 to l l.

4. In a process for removing a muscovite impurity from kaolin clay, thestep comprising providing a deflocculated aqueous pulp of kaolin claycontaining muscoviteas an impurity, conditioning said pulp with awater-soluble aluminum salt and thereafter with a small amount of acomplex phosphate ester, or salt thereof, of a nonionic surface activeethylene oxide adduct as a collector for the muscovite, and subjectingthe pulp to froth flotation, thereby producing a froth which is aconcentrate of muscovite and a tailing containing purified clay, saidphosphate ester being selected from the group consisting of monoester,diester and mixtures thereof, said nonionic ethylene oxide adductbeingthe condensation product of an organic hydroxy compound containing from8 to 50 carbon atoms and selected from the group consisting of alkylphenol and alkanol with at least one mole of ethylene oxide, saidethylene oxide adduct containing amaximum of about 50% by weight ofethylene oxide.

5. The process of claim 4'in which said phosphate ester is a mixture ofmonoester and diester, principally diester, wherein the monoester hasthe following formula:

aowmcmok o notomcmo o wherein R oleyl; and n is'4 to 5.

2. The process of claim 1 wherein said aluminum salt is added to thepulp before adding said complex phosphate ester.
 3. The process of claim2 wherein the flotation is carried out at a pH within the range of 9 to11.
 4. In a process for removing a muscovite impurity from kaolin clay,the step comprising providing a deflocculated aqueous pulp of kaolinclay containing muscovite as an impurity, conditioning said pulp with awater-soluble aluminum salt and thereafter with a small amount of acomplex phosphate ester, or salt thereof, of a nonionic surface activeethylene oxide adduct as a collector for the muscovite, and subjectingthe pulp to froth flotation, thereby producing a froth which is aconcentrate of muscovite and a tailing containing purified clay, saidphosphate ester being selected from the group consisting of monoester,diester and mixtures thereof, said nonionic ethylene oxide adduct beingthe condensation product of an organic hydroxy compound containing from8 to 50 carbon atoms and selected from the group consisting of alkylphenol and alkanol with at least one mole of ethylene oxide, saidethylene oxide adduct containing a maximum of about 50% by weight ofethylene oxide.
 5. The process of claim 4 in which said phosphate esteris a mixture of monoester and diester, principally diester, wherein themonoester has the following formula: